Present invention relates to a printing apparatus and a printing method and, more particularly to a print buffer control for a printing apparatus which comprises a print head having an array of printing elements in the same direction as a direction where recording medium is shifted.
A conventional serial printer, which moves a carriage having a print head in a horizontal direction (main-scanning direction) orthogonal to a recording-medium transferring direction (subscanning direction), has a buffer memory for storing print data, and the memory size of the buffer memory is corresponding to the recording-medium width or longer in the main-scanning direction and the length of the array of printing elements or longer in the subscanning direction.
When printing an image on a recording sheet, print data stored in the buffer memory is transferred to the print head, and at the same time, the print head is scanned in the main-scanning direction. In such printers, a printer having an ordinary printing speed has one buffer memory as described above, however, a printer for high-speed printing has two or more buffer memories to raise printing speed by alternatively using the buffer memories, i.e., writing print data into an unused buffer memory while performing printing operation.
However, in the above high-speed printer, if an effective printing area which can be printed in one scanning of the print head is increased for higher printing speed, the width of the print head in the subscanning direction becomes longer. This increases the capacity of the buffer memory. Further, the above-described double-buffer control requires at least two large capacity buffer memories. Likewise, a triple-buffer requires three large-capacity buffer memories.
In a case where this high-speed printing method is applied to a color printer, the memory capacity becomes four times larger than that in the above case, in consideration of the number of printing materials such as C (cyan), M (magenta), Y (yellow) and K (black) inks.
The increase of buffer memory capacity raises production costs, therefore, a print buffer control method which reduces costs in manufacturing a high-speed printer is highly desired.
Furthermore, in printing characters, a conventional printing operation requires a large area in a buffer memory in a case when there is a relatively large vacant area between the lines of character strings. Thus, it is highly desired to improve an utilization efficiency of buffer memory which has a size corresponding to a recording width of a print head.